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Well flow (production) test- physical characteristics -

The objective of productiontesting is to clarify theproductivity andcharacteristics of well(steam/water and gas flowrates)

1

Tetsuya YAHARA

West Japan Engineering Consultants, Inc.

Well Testing and Evaluation

Production Test

Production Characteristic (Deliverability) Curve PTS (pressure, temperature, and spinner) Logging

2

e ore mu a or

Pressure Interference Test

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Induction of Well Discharge (1) How can we produce the well? -

eam- om na e reservo r

It will be easier to start steam discharge, because it can be done by

only opening the wellhead valve.

3

Steam-dominated reservoir

Induction of Well Discharge (2) How can we produce the well? -

Water-dominated reservoir

It will be necessary to induce steam discharge from the well, applying

some kinds of method to stimulate the well, below.

1. Pressurizing the well (Air reaction)

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2. Gas lift (Air lifting)

3. Steam or two-phase injection

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Pressurizing the Well to Start Discharge

0

200

0 50 100 150 200 250 300 350 400Presssure kg/cm2 ) and Temperature )

Flowing TemperatureFlowing Pressure

400

600

800

1000MeeDehm

gStatic PressureStatic TemperatureBoiling Point CurvePressurinzing with airDepressured BoilingPoint Curve

Pressurizingwithair

5

1200

1400

1600This method is used where the air-water interface can be depressed to a level such thatthe boiling point for depth (BPD) profile from the depressed water level intersects thestable downhole temperature. (Grant, Geothermal Reservoir Engineering, 2nd p135)

Outline of the Methods for Starting Discharge

Method Outline

r ur z w w r ur z y u r r r v rhours or days to allow temperatures in the water columnto sufficiently recover, and then the wellhead valve isopened rapidly to permit discharge of compressed air,

followed by boiling geothermal fluid.

Gas l ift (Air lifting) Tubing is inserted into the well to an appropriate depth,and then air lift is started by pumping air down thetubing. Even if the pumping is stopped, self-sustained

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sc arge may occur ue o con nuous prov s on o owater from the feed zone.

Steam or two-phaseinjection

When the temperature in the well is relatively low atshallow depth, backfeed of steam or two-phase fluidfrom other production wells is useful to heat up the wellprior stating discharge by pressurizing the well.

(Grant, Geothermal Reservoir Engineering, 2nd Edition)

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Two-phase Flow Measurement Methods

Method Objective Outline Merits anddemerits

James LipPressureMethod

Roughly estimateflow rate in the Initialunstable condition

Empirical formuladeveloped by James(1966)

Versatile andeconomicalEasy to install

For proper design ofthe separator for along-term test

For highly productive two-phase geothermal wellsDifferences are within 5%to separator method, andwithin 8% to theoreticalstudy

and remove

Not quite asaccurate as theseparatormethod

Steam-Water Accurate Individual steam and Most accurate

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Method

steam and water flowrate in stablecondition for long-term testFor proper design ofthe steam turbine

system, using separatorThe overall accuracy willnot normally be betterthan 2% of the steam andwater components

friendly

(Grant, Geothermal Reservoir Engineering, 2nd Edition)

Schematic Equipment Setting

for the Lip Pressure Method Basic Equipment setting for the "Lip Pressure Method"

silencer

weir box

pressure gauge to

measure "Lip pressure"

flow

Pc

8

flow to injection well

or disposal pool

In the lip pressure method, the steam-water mixture is discharged through an appropriate sized pipe into a

silencer to separate the steam and water phases at atmospheric pressure. The lip pressure is measured at

the end of the discharge pipe. The flow rate of the steam-water mixture can be calculated based on theempirical formula developed by James.

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Schematic Equipment Setting

for the Separator Method

Orifice

P

Manometer1:DifferentialPress. between orifices

Press.

Gauge

a ve

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Separator

Production well

Manometer3 : Separator press.Manometer2: Press. prior to or ifice

Flash Chamber Weir

.

In the separator method, the flow rate of separated steam can be measured using anorifice plate and sampling the differential pressure between the front and back of theplate.

The Weir Design

b

B

H

L1 Ls L2

D

from silencer

2mm

45o

20mm

30mm

rectifier (4 plates with holes)Coverage B = 0.5 ~ 6.3 m

b = 0.15 ~ 5 m

D = 0.15 ~ 3.5 m

bD/B2>= 0.06

to pond

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H = 0.03 ~ 0.45b

1m

L1 > B+3H

Ls = about 2H

L2 > B+2H

JIS B8302-1976

The separated water can be flashed to atmospheric pressure and the waterflow rate can be measured using a weir.

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Production Characteristic (Deliverability) Curve

p

S t e a m

W a te r

MassFlow

/Enthal

T o t a l M a s s

E n t h a l p y

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W e ll H e a d P r e s s u r e

If a longer-term production test can be done, measurements are madecontinuously at a minimum of three different pressures to make the productioncharacteristics curve (the deliverability curve), for which the valve is throttled toproduce at least three different wellhead pressures.

Output (Deliverability) Curveform of the

variation of enthalpy with wellhead pressure

12(Grant, Geothermal Reservoir Engineering, 2nd Edition)

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Well Deliverability Curve of KMJ-73,

kamojang

100

KNJ73Deliverability Curve

KNJ73Deliverabilit Curve

30

40

50

60

70

80

90

ssFlowRate(ton/h)

13

0

1020

0 5 10 15 20 25

M

WellheadPressure(kg/cm2)

M. Achyan Karim et al. (2005), WGC2005

Discussion for Optimum Turbine Pressure

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Optimum turbine inlet pressure should be designed based on the deliverability curveof the production well.

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Example of PTS Logging Data

[ Casing ] [ Hole ]

Casing Program

0

500

0 1 2 3 4 5 6

Pressure (MPa)

0

100

0 50 100 150 200 250 300

0

0 50 100 150 200 250 300

Temperature ()

0

100

0 1 2 3 4 5 6

0

100

0 25 50 75 100 125 150

Spinner (rps)

17 1/2

59.1m

14

53.88m

35mm

1.375"

Cable Head

1,000

1,500

200

300

400

500

600

700

800

900

500

1,000

200

300

400

500

600

700

800

900

200

300

400

500

600

700

800

900

Depth(m)

12 1/4

510m

9 5/8

500.7m

900900900

4 1/

14")

4.

3m

54mm

2.125"

Pressure Sensor

Pressure Port

Centralizer

Temperature SensorTemperature Sensor

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2,000

1,000

1,100

1,200

,

1,000

1,100

1,200

1,000

1,100

1,2002,000

1,000

1,100

1,200

1,300

1,400

1,500

1,600

,

2,000

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,000

1,100

1,200

1,300

1,400

1,500

1,600

Feed Point

8 1/21010m

71005.7m

6 1/4

1526m

982.5m

4 1/2

1525m

Feed Point

Feed Point

54mm76mm)

Spinner Sensor

The PTS data is very usefulfor understanding theconditions in the flowingwell, such as the enteringmass flow and enthalpy ateach feed point.

Wellbore Simulation Model

with the Surrounding Formation

establishes the deliverabilitycurve of a well based on thereservoir pressure,

temperature, andpermeability-thicknessproducts (kh) at the feeddepth. The power output ofthe well can be estimated

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assuming the turbine inletpressure.

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Example of the Matching Result to the

Production Characteristic Curve

Well Name Example-1

2000

3000

y(kJ/kg)

Simulated

Field Data

Reservoir Pressure 6.86 MPaA

Reservoir Temperature 250.58

Permeability-Thickness (kh) 100.00 darcy-m

Feed Point Depth 1400.00

Liner Diameter 0.2160

Skin Factor 0.00

617.00Production CasingDepth

DiameterProduction Casing

0.2240

200

250

300

350

ate(t/h)

Simulated

Steam

Water

Total

Field Data

steam

water

0

1000

0.0 0.5 1.0 1.5 2.0

Enthalp

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0

50

100

150

0.0 0.5 1.0 1.5 2.0

Well Head Pressure ((MPaG)

Flow

R

Example of the Matching Result to the

Pressure and Temperature Profiles

0

0 50 100 150 200 250 300

Pressure (barA) / Temperature (degC)

200

400

600

800

1000

Depth(m)

18

1200

1400

1600

Pressure (Field Data) Temperature (Field Data)

Pressure (Simula ted) Temperature (Simulated)

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Interference Testing

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The pressure response at an observation well during production yields important reservoir

properties in terms of pressure interferences among the existing wells. This result can also

be utilized for numerical reservoir modeling. The observed pressure response can be used

as the matching target during the calibration process of numerical model construction.

Monitoring of Pressure Change in Reservoir

For steam-dominated reservoir,wellhead pressure indicatesalmost the reservoir pressure.

Steam-dominated reservoir

,wellhead pressure is useful toobserve the reservoir pressure.

For water-dominated reservoir,

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Water-dominatedreservoir

required to measure thepressure change over time inthe reservoir.

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Pressure Monitoring Equipment

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A capillary tubing system is used as a pressure monitoring tool that consists of a pressurechamber, capillary tube, Helium gas vessel and transducer with data recording system. Thepressure chamber is set at the depth, and then filled with Helium gas. The change in Helium gaspressure in the pressure chamber with capillary tube, which indicates reservoir pressure, istransferred to a data recording system through the transducer.

Pressure Change due to Interference,and Data Analysis

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Tsuru and Tokita (1994),15th PNOC-EDC Geothermal Conference

The pressure response at an observation well is also util ized for numerical reservoir modeling,

as the matching target during the calibration process of numerical model construction.

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Two-phasepipelineflow simulator

Changes in Reservoir during

Production and Reinjection

Wellbore Simulator

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Reservoir simulator

Dynamic change in the reservoir will occur after commissioning production and

reinjection due to interference between wells. Therefore, in order to mitigate suchimpact of interference on the well productivity, interference testing should be done

to optimize allocation of wells.

The End

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Thank you for your

attention!